The present invention relates, in general, to electronics, and more particularly, to semiconductors, structures thereof, and methods of forming semiconductor devices.
In the past, the semiconductor industry utilized various methods and structures to form power-supply controllers that were utilized to regulate an output voltage of a power supply. In some types of power supply controllers, such as hysteretic mode power supply controllers, it could be difficult to produce a power supply that had duty cycle stability. A hysteretic power supply usually is regarded as a switching power supply in which the switching frequency and duty cycle are determined by a sequential switching circuit with two states. For such power supplies, it was often necessary to use an LC output filter that had a capacitor with a high equivalent series resistance (ESR). The high equivalent series resistance (ESR) often resulted in the output voltage having a ripple voltage that was very high which could cause improper operation of the load or even damage to the load. For the case of using a capacitor with a low ESR, the low ESR reduced the ripple on the output voltage but the low ripple voltage often cause inaccurate detection of the output voltage value which could result in an irregular duty cycle and sometimes resulted in pulse skipping or cycle skipping, both of which could cause undesirable audible noise.
Accordingly, it is desirable to have a power supply controller that can operate with a range of capacitors including a low ESR capacitor or a high ESR capacitor and have a more regular duty cycle, have reduced pulse skipping, and have reduced audible noise.
For simplicity and clarity of the illustrations, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements, unless stated otherwise. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, or certain N-type or P-type doped regions, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein relating to circuit operation are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action. Additionally, the term while means that a certain action occurs at least within some portion of a duration of the initiating action. The use of the word approximately or substantially means that a value of an element has a parameter that is expected to be very close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to at least ten to fifteen percent (10%-15%) are reasonable variances from the ideal goal of exactly as described. When use in reference to a state of a signal, the term asserted means an active state of the signal and negated means an inactive state of the signal. The actual voltage value or logic state (such as a “1” or a “0”) of the signal depends on whether positive or negative logic is used. Thus, asserted can be either a high voltage or a high logic or a low voltage or low logic depending on whether positive or negative logic is used and negated may be either a low voltage or low state or a high voltage or high logic depending on whether positive or negative logic is used. Herein, a positive logic convention is used, but those skilled in the art understand that a negative logic convention could also be used. The terms first, second, third and the like in the claims or/and in the Detailed Description of the Drawings, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner.